The primary goal of this Bioengineering Research Partnership (BRP) is to demonstrate upper limb prosthesis control using our implantable myoelectric sensor (IMES) system in human amputees. By the end of this five year project period we plan to achieve our long term vision of demonstrating individual finger control of a prosthetic hand. The major factor limiting the development of sophisticated hand/arm prostheses remains the difficulty in locating and isolating sufficient numbers of command sources with which to control the many degrees-of-freedom required for a physiologically natural prosthetic hand and/or arm. While surface myoelectric (SEMG) sensing has been used for control of clinically-deployed myoelectric upper-limb prostheses, the use of multiple surface EMG signals as command sources is inherently limited by the gross nature, and lack of stability, of surface EMG signals. We believe that we can create many more EMG control sites by using IMES rather than SEMG electrodes. The primary goals of our previous BRP were to develop a myoelectric control system based upon implantable myoelectric sensors (IMES) and to demonstrate chronic functioning of this system in an animal model. These goals were accomplished. To achieve our new goal of implantation of IMES in humans and demonstration of enhanced prosthesis control, further technical development of our IMES system and human trials will be required. The specific aims for this BRP proposal are: 1) Optimization of the IMES System to Interface with Clinically Deployable Prostheses: Revise the IMES implant, IMES-TC, and multi-degree-of-freedom prosthesis controller, develop clinician tools to design coils for patients. 2) Qualification Testing of IMES Hardware and FDA Approval: Qualification of IMES Implants, External IMES Hardware, and MDOF Controller; Preparation And Submission Of FDA IDE Application For Use Of IMES In A Human Clinical Trial. 3) Implantation And Testing of The IMES System in Humans: Phase 1 - Demonstration of the IMES System as a Substitute For SEMG Control Of Standard-Of-Care Transradial Myoelectric Hand Prostheses In Transradial Amputees; Phase 2 - Demonstration of the IMES System and MDOF Controller Coordinating Volitional Movements of The Individual Fingers And Thumb of A Prosthetic Hand In Transradial Amputees.